Liquid-state switching device

ABSTRACT

A liquid-state switching device utilizes movement of a column of liquid, resulting from a change in surface tension of the liquid caused by electrocapillary action, to operate various switch means. The electrocapillary effect is induced across a single interface sets of single of mercury and an electrolyte or electrolytes. Filter partitions are installed to maintain the liquids in a proper relationship throughout variations in position of the switching device. Means are provided to assist the return of the column of liquids to their normal positions including a bias voltage, a permanently installed resistance, and/or pressurized gas pockets.

United States Patent Lucian [54] LIQUID-STATE SWITCHING DEVICE [58]Field Inventor:

Filed:

Appl.

Street, Manasquan Park, NJ. 08736 May 18, 1970 US. Cl. ..200/192,200/194, 200/211 Int. Cl. ...H01h 29/00, l-lOlh 29/06, H0lh 29/02 ofSearch...200/l52 K, 152 L, 83.34, 81.8, 200/839, 83.3; 335/49, 50, 52

References Cited UNITED STATES PATENTS 8/1955 Pettigrew et al ..200/835/1956 Bellamy ..335/49 8/1957 Boyle ..335/49 X 7/1962 Corrsin ..200/l52X 12/ 1964 Bourdel ..200/15'2 X 6/1965 Huston "ZOO/81.8

Arsene N. Lucian, 2405 Cherry 5/1966 l-lurvitz ..335/49 X 3/1967 Hurvitz..335/52 Primary Examiner-Robert K. Schacfcr Assistant ExaminerWilliamJ. Smith Attorney-Darby & Darby [57] ABSTRACT A liquid-state switchingdevice utilizes movement of a column of liquid, resulting from a changein surface tension of the'liquid caused by electrocapillary action,

to operate various switch means. The electrocapillary effect is inducedacross a single interface sets of single of mercury and an electrolyteor electrolytes. Filter partitions are installed to maintain the liquidsin a proper relationship throughout variations in position of theswitching device. Means are provided to assist the return of the columnof liquids to their normal positions including a bias voltage, apermanently installed resistance, and/or pressurized gas pockets.

24 Claims, 12 Drawing Figures PATENTEDIJBI 31 1912 sum 2 or 4 ATTORNEYS.

PATENTEDncm m2 3.701.868

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INTERFACIAL TENSION EXTERNAL VOLTAGE APPLIED ACROSS INTERFACE I NV ENTORARSENE N. LUC/AN BY 6 m w uA 7 W his ATTORNEYS.

1 LIQUID-STATE SWITCHING DEVICE BACKGROUND OF THE INVENTION Thisinvention relates to liquid-state switching devices and, in particular,to novel and highly effective switching devices that' respond toelectrocapillary forces generated by electrical inputs of very lowvoltage and current.

Many difficulties, which are well known to those versed in the switchingand relay arts, are encountered in constructing electrical switchingdevices which dependably actuate contact means in response to very lowinput voltages and currents. The common electromechanical relay, forexample, has been designed to respond to very low voltages; however,either the actuating current is high or the required mechanism is sodelicate that the dependability of the switch is relatively low. At lowinput voltages and currents, the available actuating power is low, andthus it has been difficult to construct a switch having a short responsetime. In switching mechanisms which use movable contacts to break theelectrical circuit, problems have also been encountered with contactarcing and deterioration from exposure to the atmosphere, andencapsulation of the contact means has provided additional problems,such as poor serviceability and excess bulk. Often, the solution to oneproblem leads to further difiiculties in another area.

SUMMARY OF THE INVENTION There is provided in accordance with thepresent invention a novel and useful switching device that is highlysuitable for actuation by an electrical input of low voltage and verylow current. The invention applies the well-known principles ofelectrocapillary phenomena, which involve interactions between a doublelayer of electrical charges at a single interface between twopartiallyconducting liquids in contact with each other in a capillarytube, and the surface tension of the liquids. The result of theseinteractions is a change in surface tension at the single interface ofthe liquids when an electromotive force of low voltage, such as smallfractions of a volt, and negligible current are impressed across theinterface. A conducting liquid and an electrolyte immiscible with theconducting liquid are placed in contact in a capillary tube and asuitably low voltage is applied to generate a motive force which is thenutilized to actuate various switch means. It is a significant feature ofthe invention that the switching operations are accomplished without theaid of externally imposed electromagnetic or electrostatic fields.Various switch means are provided which are susceptible to directhydraulic actuation by one of the liquid phases comprising the switch.Since intermediate mechanical components are eliminated, thedependability of the switch is increased.

The switch according to the invention also includes sealed switch meansto prevent atmospheric contamination. Furthermore, some embodimentsemploy a liquid contactor to minimize malfunctions caused by arcing thepitting of the contacts. To shorten the total response time of theswitching device, various means are provided to assist the return of thecapillary columns to their normal positions including enclosed gaspockets which exert a slight counter pressure on the liquids, a biasvoltage which operates on removal of the ,2 control voltage to quicklyreturn the interfacial potential to its original value, and a resistor,permanently installed across the control contacts, to dissipate thecounter electromotive, or back e.m.f., force developed upon actuation ofthe switch. I

BRIEF DESCRIPTION OF THE DRAWINGS An understanding of additional aspectsof the invention may be gained from a consideration of the followingdetailed description of several representative embodiments thereof, inconjunction with the appended figures of the drawing, wherein:

FIG. 1 is an elevation view in enlarged longitudinal section of a priorart'device used to illustrate the principles of operation of the subjectinvention;

FIGS. 2 through 8 are views similar to FIG. 1 showing variousembodiments of the invention;

FIGS. 9 through 11 are schematic representations of electrical biasingmeans;

FIG. 12 is a representative electrocapillary curve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference is first made to FIG.1 which shows a prior art device for an explanation of theoreticalbackground to aid in the understanding of the subject invention. FIG. 1shows an envelope 10 of suitable dielectric material, which may, forexample, be glass. The envelope consists of three functional sections: atube 12, a reservoir 14, integrally fused with the tube at one endthereof and having a common fluid path 15 with the tube, and a reservoir16, integrally fused with the tube 12 at the other end thereof, and alsohaving a common fluid path 17 with the tube. The tube 12 has a bore withtransverse dimensions which are of capillary magnitude; however, theinterior transverse dimensions of the reservoir 14 are not critical andmay be greater than the corresponding dimensions of the capillary tube12.

The envelope contains a column of mercury 18, which partially fills thereservoir 14 and extends into the capillary tube 12, a first globule ofmercury 20, which is located in the capillary tube section, and anelectrolyte 22, such as acidulated water, which forms an interface ormeniscus 19 with the column of mercury 18. The electrolyte alsomaintains the mercury globule 20 in a spaced relationship tothe columnof mercury 18. The envelope 10 also contains a second globule of mercury24, which is spaced from the globule 20 by a dielectric liquid 26, whichmay, for example, be transformer oil, and a third globule of mercury 28,which is spaced from the globule 24 by a similar dielectric liquid 30.Other suitable metallic liquids may be substituted for the mercury;however, the metallic liquid and the electrolyte must be immiscible.

Excessive movement of the globule 28 to the right as represented in FIG.1 is prevented by a barrier 32, comprising, for example, a spring orgauze pad. A pair of electrodes 34 and 36 are integrally fused in theenvelope, the electrode 34 contacting the mercury colunm 18 and theelectrode 36 contacting the mercury globule 20. Integrally fused intothe capillary tube 12 are a plurality of electrodes 38,40,42,and 44 toprovide two normally-opened circuits.

also to aid in the return of the system to its normal state.

The electrocapillary effect is well known, and derives from interactionsbetween interfacial potential and surface tension. It has beentheoretically established, as a corollary of the Helmholtz double-layertheory, that a double layer of opposite electrical charges exists at asingle interface of a metal and an electrolyte in contact, and that themetal is positively charged with respect to the electrolyte. With noexternal voltage applied, these two oppositely charged layers attracteach other, and remain in equilibrium. It has been observed that if thissteady-state charge distribution is altered by applying an externalvoltage across the single interface, the interfacial tension isconcurrently altered. It is this change in surface tension of theliquids which causes movement of the liquids in the switch according tothe invention.

The relationship between the voltage applied across the single interface19 and the surface tension of the mercury column 18 is considered withreference to the curve in FIG. 12. This curve corresponds to the knownelectrocapillary curve; however, the ordinate corresponds to the surfacetension of the mercurycolumn rather than the often-depicted height of acolumn of liquid supported by a capillary surface. The abscissacorresponds to the control voltage applied across the interface 19 withthe polarity of the voltage being measured with reference to the mercurycolumn 18.

For a mercuryelectrolyte single interface to which an increasinglypositive voltage is applied (thus making the mercury surface a cathode),it is apparent from the curve that the surface tension initiallyincreases, which corresponds to the reduction of the positive charge onthe mercury surface. The surface tension reaches a maximum value,represented by the apex of the electrocapillary curve, when the electronflow to the mer cury side of the interface reduces the positive chargeon the mercury surface to zero. Further increase in the applied voltagecauses the mercury surface to become increasingly negative with respectto the electrolyte surface and the surface tension decreases. Ifthevoltage is reversed and the mercury is made an anode, no suchneutralizing occurs, the interfacial potential increases in proportionto the applied voltage and the surface tension decreases proportionallyto the magnitude of the applied voltage.

Four modes of switch operation are possible. First, the mercury can bemade a cathode with a relatively small voltage applied, whereby theinterfacial tension increases and there is movement of the interface 19to the left as represented in FIG. 1. In the second mode, the mercurycan bemade an anode and upon application of any magnitude of voltage theinterfacial tension decreases and there is movement to the right asrepresented in FIG. 1. In the third mode of operation,

the mercury can again be made a cathode with, however, a large voltageapplied, so that the interfacial tension first increases and thendecreases, thus resulting in an initial movement to the left followed bymovement to the right as represented in FIG. 1. An additional, fourth,mode of operation is available if a steady-state bias voltage is appliedacross the mercury-electrolyte interface, with a control voltage appliedin series to vary the total applied interfacial potential from thesteady-state bias voltage. In this fourth mode the value of themercury-electrolyte interfacial tension is a function of the sum of thebias voltage and the control voltage. For example, if the bias voltagelevel is set so that for the steady-state condition the switch isoperating at the apex of the electrocapillary curve shown in FIG. 12 (byreducing the positive charge distribution on the mercury surface tozero), then the application of a control voltage in series with the biasvoltage in either'a positive or a negative direction decreases theinterfacial tension, since, for both voltages taken together, the switchis caused to operate at some point not at the apex of theelectrocapillary curve. A bias voltage is also employed in a secondmanner according to the invention, not in series with the controlvoltage, but supplementary to it to cause the interface to more quicklyreturn to the steady-state position after the control voltage isremoved. The principle of operation and ef' feet on the switch of a biasvoltage in the last-mentioned application is analogous to theapplication of a voltage in any of the first three modes presentedabove.

Although it is possible to operate a device of this kind in which amercury column is made an anode, such as in mode two above, chemicalreactions may develop which render such a construction less desirablethan one wherein the mercury column is made the cathode, e.g., oxidationof the mercury surface (see Dole, M., Principles of Experimental andTheoretical Electrochernistry,N.Y., McGraw-Hill Book Company,. 1935,Chapter 27, p. 467), or formation. of mercurous sulfate (see Findlay,A., Practical Physical Chemistry, London, Longmans, Green & Co.,l91l, p.198). Such chemical reactions will detract from the reliability of thedevice. It is realized that according to the embodiment shown in FIG. 1the double interface 21, which is defined between the electrolyte 22 andthe mercury globule 20, constitutes a second mercury-electrolyteinterface in which the mercury globule 20 must be an anode if themercury column 18 is made a cathode. This presents the disadvantagesabove discussed for anode operation, and, in accordance with theinvention, a construction substantially reducing the problems inherentin necessarily operating one of the transfer interfaces as an anode isshown in FIGS. 2-8 which are discussed hereafter.

Returning to FIG. 1, the switch is preferably operated with the mercurycolumn 18 made a cathode and values of control voltage are applied whichare sufficiently small that the interfacial tension increases in directrelationship to the magnitude of the applied voltage.

Upon application of such a preferred voltage, the mercury interface 19moves to the left as represented in FIG. 1 and a differential pressureis exerted on the liquid in the capillary tube 12, causing such liquidto move towards the left. Since the interior of the tube 12 is ofcapillary transverse dimensions, no fluid or gas can by-pass theglobules of mercury 24 and 28. The fluid movement thus causes themercury globule 24 to move towards the left, thereby completing anelectrical path between the electrodes 38 and 40, and also causes themercury globule 28 to move a similar distance to the left to complete anelectrical path between the electrodes 42 and 44. The mercury globule 20is positioned so that when it is at maximum operative displacement tothe left or to the right, and for any position therebetween, it is incontinuous contact with the electrode 36. FIGS. 2 through 8 illustratemeans according to the present invention by which the pressure exertedby the moving mercury column actuates various switching means. FIGS. 2through 8 also illustrate various means by which the electrocapillaryswitch may be designed to decrease susceptibility to positionalvariations. The embodiments of these figures also show means forapplying the proper polarity voltage to the electrolyte mercury singleinterface which substantially avoids the disadvantages presented abovewhich are associated with anode operation of an interface.

In the embodiment shown in F IG. 2, the envelope 10 comprises thecapillary tube 12, a reservoir 56, integrally fusedwith the capillarytube at one end thereof and having a common fluid path 57 with the tube,a reservoir 58, integrally fusedwith the tube 12 at the other endthereof and also having a common fluid path 59 with the tube, asleeve60, integrally fused with the reservoir 56 and having a common fluidpath 61 therewith, and a reservoir 62, integrally fused with thereservoir 58 and having a common fluid path 63 therewith.

The mercury column 18 substantially fills the reservoir 56, and extendsinto and partially fills both the capillary tube 12 and the sleeve 60.The electrolyte 22 substantially fills the reservoir 58, and extendsinto and partially fills the capillary tube 12, forming an interface 19in the capillary tube with the mercury column 18. A quantity of gas,which may be air, substantially fills the reservoir 62, preferably at apressure slightly greater than atmospheric, creating a gas pocket 64therein. The electrode 34 is integrally fused into the envelope 10 atthe reservoir 56, and contacts the mercury column 18. A mercury pool 66is contained within the reservoir 58 and contacts the electrolyte 22. Aterminal 68 is integrally fused into the envelope 10 at the reservoir58, and contacts a mercury pool electrode 66. It is an important featurein this embodiment that the interior dimensions of the reservoir 58 aresufficiently large and the quantity of mercury 66 sufiiciently greatthat the surface-area of the interface 65 is large compared to thesurface area of the interface 19. This construction yields anon-polarizable electrode so that the undesirable effects of operatingthe metallic liquid at interface 65 in an anode configuration aresubstantially reduced, and the efficacy of the electrode to establishthe desired potential in the electrolyte is increased. Similarnon-polarizable electrodes may be employed, and it is apparent to oneskilled in the art that the mercury 66 may readily be substituted byother materials, for example mercurous chloride, in which case a calomelelectrode is obtained.

A filter partition 70 is positioned in the fluid path 63 between thereservoir 58 and the reservoir 62 and sub stantially fills the path 63so that all fluid flow must pass through the filter partition 70. Thefilter partition is impervious to the electrolyte 22 and completelypervious to the gas contained in the gas pocket 64. A second filterpartition 72 is positioned in, and substantially occopies, the fluidpath 59 so that all fluid flow must pass through the filter partition72. The filter partition 72 is impervious to mercury and completelypervious to the electrolyte. The filter partitions 70 and 72 increasethe positional stability of the switching device by restricting themotion of the interface 19 to the capillary tube 12, thereby preventingthe flow of the mercury or electrolyte to an improper cavity.

An insulating plunger 74 is carried within the sleeve 60 and travels inan axial direction therewithin. The mercury column 18 contacts theinsulating plunger 74, which substantially occupies the interiortransverse area of the sleeve 60 so that no mercury can by-pass theplunger 74 at the bearing surface between the plunger and the sleevewall. An insulating spacer 78 seals the open end of the sleeve'60 andcarries a pair of spaced electrodes 82 and 84. A cavity 80 is locatedwithin the sleeve 60 between the plunger 74 and the spacer 78.

The electrodes 82 and 84 extend through the spacer 78 into the cavity80. When a suitably low voltage of preferred polarity is impressedacross the electrodes 34 and.68 the resultant electrocapillary forcecauses the mercury column 18 to exert a pressure on the plunger 74 tocause the plunger to move upward, contact, and deflect the electrode 84at a curved end 85. The electrode 82 is positioned in the cavity 80 sothat the deflection of the electrode 84 causes it to contact theelectrode 82 to complete an electrical circuit between the electrodes 82and 84. I

The embodiment shown in FIG. 3 is similar in operation to FIG. 2, but anoverlapping contact arrangement is shown. A housing 86 is formedintegrally with the sleeve 60. A plurality of spaced electrodes 88, 90,92, and 94 pass through, and are affixed to the housing 86. Theinsulating plunger 74 travels longitudinally in the sleeve 60 and iscaused to move by the electrocapillary force produced as described inconjunction with FIG. 2. The plunger 74 firstcontacts the electrode 88and deflects it to contact the electrode 90,"thus completing anelectrical circuit between the electrodes 88 and 90. As additional forceis exerted on the plunger 74 by the mercury column 18, the plunger movesfurther outward, causing the electrode 90 to deflect. The electrode 90,through an insulating spacer 96, deflects the electrode 92, which thencontacts the electrode 94 to complete an electrical path between theelectrodes 92 and 94. When the plunger 74 retracts into the sleeve 60,the electrodes 92 and 94 break contact prior to the electrodes 88 and90, thus creating an overlapping sequence of operation. It is apparentto a person skilled in the art that the electrodes 88, 90, 92, and 94may readily be rearranged to provide simultaneous operation.

FIG. 4 illustrates another switching means. A hollow resilient coil 98,which may be glass, is carried within the sleeve 60. One end 97 of theglass coil 98 is joined to the wall of the reservoir 56 with theinterior of the reservoir 56 in fluid communication with the cavity ofthe glass coil 98. The other end 99 of the glass coil 98 is sealed. Apair of spaced electrodes 100 and 102 are mounted by the housing 86 inoperative relationship to the glass coil. The mercury column 18substantially fills the glass coil 98, as well as filling the reservoir56 and partially filling the capillary tube 12. When a control voltageis applied to the electrodes 34 and 68 as described in conjunction withFIG. 2, the electrocapillary force produced causes the mercury column 18to exert an internal pressure on the glass coil 98, thereby causing theglass coil to increase in length in the direction of the axis of thesleeve 60. As the glass coil 98 increases in length, it contacts theelectrode 100 and causes it to deflect and contact the electrode 102 tocomplete an electrical circuit between the electrodes 100 and 102.

FIG. is similar in operation to FIG. 4, except that a resilient bellows110, which preferably is metal, but which may also be glass or rubber orneoprene, replaces the glass coil 98. Similarly to the glass coil 98,the metal bellows 110 is carried within the sleeve 60 and has one end111 attached to the wall of the reservoir 56 by means preventing theby-pass of fluid between the bellows and the wall. The bellows 110 is influid communication with the reservoir 56, and is sealed at its otherend 113. When a proper control voltage is applied to the electrodes34and 68, the resultant electrocapillary force increases the internalpressure of the mercury column 18 to cause the bellows to lengthen inthe direction of the axis of the sleeve 60. As the bellows 110 increasesin length, it contacts the electrode 100 and deflects it to contact theelectrode 102, thus completing an electrical circuit between theelectrodes 100 and 102.

In the embodiment shown in FIG. 6, a sleeve 112 is formed integrallywith the reservoir 56 and has a common fluid path 113 therewith. Themercury column 18 extends into and partially fills the sleeve 112, aswell as substantially filling the reservoir 56 and partially filling thecapillary tube 12. An insulating plunger 114 travels longitudinallywithin the sleeve 112, and is in intimate contact with the mercurycolumn 18. The plunger 114 substantially occupies the transverse area ofthe housing 112 to prevent by-pass of mercury between the plunger andthe housing wall. A pair of electrodes 116 and 118 pass through, and areaffixed by, the sleeve 112. A bellows 120, which may, for example, bemetal, is contained within the housing 112 and is integral with theelectrode 118. An insulating spacer 122 maintains the bellows 120 in aspaced relationship to the electrode 1 16. When a proper voltage isapplied to raise the interfacial tension of the mercury column 18, theelectrocapillary force causes the plunger 114 to travel upward in thehousing 112 and contact the bellows 120. Further motion of the plunger114 causes the bellows 120 to contact the electrode 116, therebycompleting an electrical circuit between the electrodes 116 and 118. i

In the embodiments of the invention shown in FIGS. 2-6, a singlecapillary tube 12 is provided having reservoirs located at either end.FIG. 7 shows an embodiment of the invention in which theelectro-capillary force is generated by a pair of interfaces inparallel. A mercury reservoir 140 and an electrolyte reservoir 142 areprovided which are substantially identical to the reservoirs 56 and 58respectively of FIG. 2; however, it is understood that any of therespective reservoirs in FIGS. 2-6 may readily be substituted. A tube144, which may, for example, be glass, extends between and connectsreservoirs and 142. Extending through the tube 144 are two spacedpassageways 146 and 148, each passageway communicating at one end withthe interior of reservoir 140 and at the other end with the interior ofreservoir 142. The passageways 146 and 148 each duplicate the bore oftube 12 and accordingly each has transverse dimensions which are ofcapillary magnitude and carries a mercury-electrolyte interface, 150 and152 for passageways 146 and 148 respectively. It is understood that theembodiment shown in FIG. 7 is merely exemplary, it being clear that anynumber of capillary passageways may be provided in the tube, and thatthe relative position of the passageways need not be parallel, but maybe oblique, and that the respective lengths of the passageways may varysubstantially depending on the path. 7

When a proper control voltage is applied to electrodes 34 and 68 themovement of each of the interfaces 150 and 152 will be approximately thesame as the movement experienced for the interface 19 in the figurespreviously considered. Since interfaces 150 and 152 undergo simultaneousdisplacement, the total fluid displaced is multiplied by a factorcorresponding to the number of passageways, in this case two, over thefluid displaced by a single capillary interface as in the previouslyconsidered embodiments. Therefore, the travel of the plunger 74 isapproximately twice that experienced previously and the dependability ofthe switch is accordingly increased.

Another embodiment of an'electrocapillary switch is shown in FIG. 8. Aswith the switchshown in FIGS.

2-7, a suitable control voltage is applied to the terminals 68 and 154to cause movement of the interface 156 to the left as shown in FIG. 8.Movement of the interface 156 to the left, also causes globule ofmercury 158 to move to the left. Three insulating spherical balls 160,which may be glass, are arranged within the capillary tube in adjacentrelation to each other and to the mercury globule 158. The glass balls160 substantially occupy the interior transverse dimensions of thecapillary tube; however, it is understood that the glass balls may be ofany diameter smaller than the interior transverse dimensions of thecapillary tube provided that the motion of globule 158 is effectivelytransmitted to globule 162 as next described. Upon movement of theglobule 158 to the left, it exerts a pressure on the glass balls 160which in turn exert pressure to cause the mercury globule 162 to moveto-the left and complete an electrical circuit between the electrodes164 and 166.

FIG. 8 also shows an enclosed gas chamber 168 located to the left of themercury globule 162. The gas in the chamber is slightly compressed bythe globule 162 when no voltage is applied across the electrodes 68 and154. Upon movement of the interface 156 to the left as above described,the gas in the pocket 168 is further compressed, and upon removal of thevoltage, the gas pocket exerts a reactive pressure to restore themercury globule 162 back to its normal position.

As mentioned above in conjunction with the modes of operation of anelectrocapillary switch, a bias voltage may be applied across themetal-electrolyte interface to facilitate the return of the interface toits normal position after removal of a control voltage. FIG. 9

shows a representative embodiment for applying such a bias voltage, itbeing understood that any of the switch arrangements shown in FIGS.2-8may be utilized, and that a switch outline similar to FIG. 2 is shownby way of example. In the switch according to FIG. 9, the polarity ofapplication of the control voltage is indicated by the positive andnegative signs 170 and 172. A DC bias voltage source 174, which may be abattery, is connected in series with a resistance 176 across theterminals 34 and 68. For a control voltage of approximately one-halfvolt, the bias voltage is approximately 0.1 volt, and the value of theresistance 176 is approximately lOK ohms. The polarity of the battery174 is opposite that of the control voltage as indicated "by thepositive and negative signs 178 and 180. For a properly selected valueof resistance 176 itmay be seen from an analysis of the network that theeffect of the bias voltage 174 may be ignored when a control voltage isapplied to the terminals 34 and 68. Upon removal 'of the controlvoltage, the bias voltage 174 becomes effective to apply a reversepotential across the interface to facilitate the return of the interfaceto the original position.

It is a further feature of the invention that the return of theinterface may also be facilitated by permanently installing a resistance186, which may be in the range of 2K-3K ohms, across the terminals 34and 68 as shown in FIG. 10. The resistance 186 facilitates the return ofthe interface to normalby dissipating the counter electromotive force(back e.m.f.) developed when a'control voltage is applied across theterminals 34 and 68, analogously to the resistance braking employed inelectric motors, or breaking the closed circuit of an electrolyticprimary cell.

The bias voltage 174 may also be applied to terminals 34 and 68intermittently and without the resistance 176 (FIG. 9) as shown in FIG.11. The intermittent application enables the bias voltage to cause theinterface to return to its original position after removal of thecontrol voltage without interfering with the control voltage during itsapplication. A timer 188 for accomplishing this type of operation iscommonly known in the art and is described as having a time delay uponde-energization. Upon application of the control voltage, the timercontacts open and the bias voltage 174 is removed from the terminals 34and 68. Upon removal of the control voltage a timed contact closes andthe bias voltage 174 is applied across terminals 34 and 68 until eitherthe timed contact opens or, alternatively, until the control voltage isreapplied.

While the invention has been described in terms of the above preferredembodiments, it is recognized that others skilled in .the art may applythe novelfeaturejs in a wide variety of combinations and switchingarrangements without departing from the spirit and scope of theinvention. For example, the hollow glass coil 98 of FIG. 4 may beapplied in FIGS. 2, 3, 6, or 7 to actuate the contact means thereincontained. Another readily obtained modification of the aboveembodiments involves substitution of normally-closed contactconfigurations for the normally-open configurationsshown. A stillfurther modification, for example, is to vary the interior transversearea of the capillary tube 12, within capillary dimensions, whereby theinterface between the mercury column 18 and the electrolyte22 moves in aportion of the capillary tube havingasmaller transverse area than thatportion carrying the mercury globules, thereby facilitating installingof the electrodes into the envelope. Therefore, the invention is to beconstrued as including all of the embodiments thereof within the scopeof the appended claims.

I claim:

1. A liquid-state switching device for electrical circuits, comprising:

an envelope including a tube portion having capillary transverseinterior dimensions;

a metallic liquid contained within said envelope and extending into saidtube portion;

an electrolyte contained within said envelope and extending into saidtube portion, said metallic liquid and said electrolyte being immisciblein each other and forming a' single interfacein said capillary tubeportion;

means for applying an electromotive force across said metallic liquidand said electrolyte effective't o change the interfacial tension ofsaid liquids at said single interface whereby electrocapillary movementof said interface isinduced; and

contact means including a plurality of spaced globules of a thirdconducting liquid located within said capillary tube portion, aplurality of pairs of spaced electrodes operatively associated with arespective globule of said third electrically conductive'liquid so thatsaid motion of said interface causes each globule of conducting liquidto close an electrical circuit between the respective pair ofelectrodes, and at least one quantity of gas operatively located betweenat least one pair of said globules, whereby the globule of said pair ofglobules which is located farther from said interface actuates anelectrical circuit between the respective pair of spaced electrodes atsome time subsequentto the time at which the globule of said pair ofglobules which is located nearer said interface actuates an electricalcircuit between the respective pair of spaced electrodes.

2. A liquid-state switching device for electrical circuits, comprising:I

an envelope including a tube-portion having capillary transverseinterior dimensions;

a metallic liquid contained within saidenvelope and extending'into saidtube portion;

an electrolyte contained within said envelope and extending into saidtube portion, said metallic liquid and said electrolyte being immisciblein each other and forming a single interface in said capillary tub meansfor applying an electromotive force across said metallicliquid and saidelectrolyte effective to change the interfacial tension between saidliquids whereby electrocapillary movement of said single interface isinduced;

contact means having at least one movable element for actuatinganelectrical circuit; and

translating means for moving said movable element rmponsive to movementof said single interface including a hollow resilient coil closed at oneend, the interior of said coil being in fluid communication with saidinterface, whereby movement of said interface causes said coil to changein length in the axial direction to actuate said contact means.

3. A switching device according to claim 2, wherein said hollowresilient coil is made of glass,

4. A liquid-state switching device for electrical circuits, comprising:

an envelope including a tube portion having capillary transverseinterior dimensions;

a metallic liquid contained within said envelope and extending into saidtube portion;

an electrolyte contained within said envelope and extending into saidtube portion, said metallic liquid and said electrolyte being immisciblein each other and forming a single interface in said capillary tube;

means for applying an electromotive force across said metallic liquidand said electrolyte effective to change the interfacial tension betweensaid liquids whereby electrocapillary movement of said interface isinduced;

contact having at least one movable element for ac tuating an electricalcircuit and translating means for moving said movable element responsiveto movement of said single interface.

5. A switching device according to claim 4 wherein said translatingmeans includes a resilient bellows having one side in fluidcommunication with said single interface.

6. A liquid-state switching device for electrical circuits, comprising:

an envelope including a tube portion having capillary transverseinterior dimensions;

a metallic liquid contained within said envelope and extending into saidtube portion;

an electrolyte contained within said envelope and excontact means havingat least one movable element 4 for actuating an electrical circuit andtranslating means for moving said movable element responsive to movementof said single interface including at least one substantially sphericalball made of a insulating material.

7. A switching device according to claim 6, wherein said spherical ballis located within said capillary tube portion, the diameter of said ballbeing less than said capillary tubes so that said ball may travellongitudinally within said capillary tube responsive to movement of saidinterface.

8. A liquid-state switching device for electrical circuits, comprising:

an envelope including a tube portion having capillary transverseinterior dimensions;

a metallic liquid contained within said envelope and extending into saidtube portion;

an electrolyte contained within said envelope and extending into saidtube portion, said metallic liquid and said electrolyte being immisciblein each other and having a single interface in said capillary tube;

a. source of electromotive force;

first and second substantially polarization resistant electrodes forapplying said electromotive force to and across said metallic liquid andsaid electrolyte respectively, said second electrode comprising acalomel electrode, whereby the interfacial tension between said liquidand said electrolyte is changed so that electrocapillary movement ofsaid interface is caused; and

contact means having at least one movable element actuated by saidmotion of said interface.

9. A switching device according to claim 8, wherein said envelopeincludes a reservoir, and said electrolyte is contained within saidreservoir and extends into said capillary tube, and wherein said secondelectrode has a second interface in said reservoir with saidelectrolyte, the surface area of said second interface being large withrespect to the first interface between said electrolyte and saidmetallic liquid, whereby a substantially non-polari2able electrode isprovided.

10. A liquid-state switching device for electrical circuits, comprising:

an envelope including a tube portion having capillary transverse andinterior dimensions;

a metallic liquid contained within said envelope and extending into saidtube portion;

an electrolyte contained within said envelope and extending into saidtube portion, said metallic liquid and said electrolyte being immisciblewith each other and forming a single interface in said capillary tube;

means for applying a first electromotive force across said metallicliquid and said electrolyte effective to change the interfacial tensionbetween said metallic liquid and said electrolyte and cause movement ofsaid single interface; contact means having at least one movable elementactuated by said motion of said interface; and

means efiective upon removal of said first electromotive force forcausing return movement of said interface to an initial positionoccupied prior to application of said first electromotive force, wherebythe response timeof the switching device is improved.

11. A switching device according to claim 10, wherein said means forcausing return movement of said interface includes means for applying asecond electromotive force across said metallic liquid and saidelectrolyte to cause movement in a direction opposite to said firstelectromotive force.

12. A switching device according to claim 11, wherein said means forcausing return movement of said interface further includes resistancemeans in series with said means for applying a second electromotiveforce of sufficiently high value that the electrocapillary effect due tosaid second electromotive force is negligible compared to theelectrocapillary effect due to said first electromotive force when bothsaid first electromotive force means and said second electromotive forcemeans are operatively connected across said interface.

13. A switching device according to claim 11, wherein said means, forapplying a second electromotive force across'said first and secondliquids includes an electrical control circuit operatively connected tointerlock said second electromotive force responsive to ILL applicationof said first electromotive force and to apply said second electromotiveforce for a predetermined length of time responsive to removal of saidfirst electromotive force.

14. A switching device according to claim 10, wherein said means forcausingreturn movement of said interface includes a resistanceoperatively connected across said first and second electrodes.

15. A switching device according to claim 10, wherein said means forcausing return movement of said interface includes at least one quantityof gas contained within said envelope and operatively associated withsaid interface to change volume responsive to movement of said interfacecaused by said first electromotive force means and to exert a reactionforce on said interface effective to cause said interface to return tosaid initial position upon removal of said first electromotive forceapplying means.

16. A switching device according to claim 15, wherein said quantity ofgas is initially at a pressure greater than atmospheric, and whereinmovement of said interface responsive to said first electromotiveforcemeans compresses said quantity of gas.

17. A liquid-state switching device for electrical circuits, comprising:

an envelope including a tube portion having capillary transverseinterior dimensions;

a first conducting liquid containedwithin said envelope and extendinginto said tube portion;

a second conducting liquid contained within said envelope and extendinginto said tube portion, said first and second liquids being immisciblein each other and forming a single interface in said capillary tube;

means for applying an electromotive force across said first and secondliquids effective tochange the interfacial tension between said firstand second liquids and cause movement of said single interface and saidfirst and second liquids;

contact means having at least one movable element actuated by saidmotion of said interface; and

filter means operatively associated with said first and second liquidsfor restricting said motion of said interface to said capillary tube.

18. A switching device according to claim 17, wherein said envelopeincludes first and second reservoirs, said first reservoir is joinedwith said capillary tube at one end thereof and has a common fluid paththerewith, said electrolyte extends into and partially fills said firstreservoir, and wherein said second reservoir is joined with said firstreservoir and has a common fluid path therewith, and further comprisinga gas filling said second reservoir, a first filter partition mounted inthe fluid path between said capillary tube and said first reservoir andsubstantially separating said capillary tube and said first reservoirfrom'each other, said filter partition being pervious to saidelectrolyte and impervious to said metallic liquid, and a second filterpartition mounted in the fluid path between said first reservoir andsaid second reservoir and substantially separating said first reservoirand said second reservoir from each other, said second filter partitionbeing pervious to said gas and impervious to said electrolyte.

19. A liquid-state switching device for electrical cira e l o p e iicluding a plurality of passageways having capillary transverse interiordimensions;

a first conducting liquid contained within said envelope and extendinginto the respective passageways; v

a second conducting liquid contained within said envelope and extendinginto the respective passageways, said first and second conductingliquids being immiscible with each other and forming a single interfacewith each other in each of said plurality of passageways respectively;

vmeans for applying an electromotive force across said first and secondliquids effective to'change the interfacial tension between said firstand second liquids at each interface in the respective passageways andcause movement of each said interface, whereby motion of said first andsecond liquids is caused responsive to motion of said plurality of saidinterfaces; and

contact means having at least one movable element actuated by saidmotion of said first and second liquids.

20. A switching device according to claim 19, wherein each saidcapillary passageway having one and only one interface between saidfirst 'and said second liquids.

21. A switching device according to claim 19 further comprising filtermeans operatively associated with said first and second liquids forrestricting said motion of said interfaceto said capillary tube.

22. A liquid-state switching'device for electrical circuits, comprising:

an envelopeincluding a tube portion having capillary transverse andinterior dimensions; a metallic liquid contained within said envelopeand extending into said tube portion; an electrolyte contained withinsaid envelope and extending into said tube portion, said metallic liquidand said electrolyte being immiscible with each other and forming asingle interface in said capillary tube; means for applying a firstelectromotive force across said metallic liquid and said electrolyteeffective to change the interfacial tension between said metallic liquidand said electrolyte and cause movement of said single interface;

switching circuit means having portions located within said envelope;and

means responsive to the movement of said interface for changing thestate of said switching circuit means coacting with the portions of theswitching means within said envelope.

23. A switching device as in claim 22 further comprising a source offirst electromotive force, said electromotive force applied across saidmetallic liquid and said electrolyte so that the electrolyte is positivewith respect to said metallic liquid.

24. A switching device as in claim 23 wherein said metallic liquid ismercury.

1. A liquid-state switching device for electrical circuits, comprising:an envelope including a tube portion having capillary transverseinterior dimensions; a metallic liquid contained within said envelopeand extending into said tube portion; an electrolyte contained withinsaid envelope and extending into said tube portion, said metallic liquidand said electrolyte being immiscible in each other and forming a singleinterface in said capillary tube portion; means for applying anelectromotive force across said metallic liquid and said electrolyteeffective to change the interfacial tension of said liquids at saidsingle interface whereby electrocapillary movement of said interface isinduced; and contact means including a plurality of spaced globules of athird conducting liquid located within said capillary tube portion, aplurality of pairs of spaced electrodes operatively associated with arespective globule of said third electrically conductive liquid so thatsaid motion of said interface causes each globule of conducting liquidto close an electrical circuit between the respective pair ofelectrodes, and at least one quantity of gas operatively located betweenat least one pair of said globules, whereby the globule of said pair ofglobules which is located farther from said interface actuates anelectrical circuit between the respective pair of spaced electrodes atsome time subsequent to the time at which the globule of said pair ofglobules which is located nearer said interface actuates an electricalcircuit between the respective pair of spaced electrodes.
 2. Aliquid-state switching device for electrical circuits, comprising: anenvelope including a tube portion having capillary transverse interiordimensions; a metallic liquid contained within said envelope andextending into said tube portion; an electrolyte contained within saidenvelope and extending into said tube portion, said metallic liquid andsaid electrolyte being immiscible in each other and forming a singleinterface in said capillary tube; means for applying an electromotiveforce across said metallic liquid and said electrolyte effective tochange the interfacial tension between said liquids wherebyelectrocapillary movement of said single interface is induced; contactmeans having at least one movable element for actuating an electricalcircuit; and translating means for moving said movable elementresponsive to movement of said single interface including a hollowresilient coil closed at one end, the interior of said coil being influid communication with said interface, whereby movement of saidinterface causes said coil to change in length in the axial direction toactuate said contact means.
 3. A switching device according to claim 2,wherein said hollow resilient coil is made of glass.
 4. A liquid-stateswitching device for electrical circuits, comprising: an envelopeincluding a tube portion having capillary transverse interiordimensions; a metallic liquid contained within said envelope andextending into said tube portion; an electrolyte contained within saidenvelope and extending into said tube portion, said metallic liquid andsaid electrolyte being immiscible in each other and forming a singleinterface in said capillary tube; means for applying an electromotiveforce across said metallic liquid and said electrolyte effective tochange the interfacial tension between said liquids wherebyelectrocapillary movement of said interface is induced; contact havingat least one movable element for actuating an electrical circuit andtranslating means for moving said movable element responsive to movementof said single interface.
 5. A switching device according to claim 4wherein said translating means includes a resilient bellows having oneside in fluid communication with said single interface.
 6. Aliquid-state switching device for electrical circuits, comprising: anenvelope including a tube portion having capillary transverse interiordimensions; a metallic liquid contained within said envelope andextending into said tube portion; an electrolyte contained within saidenvelope and extending into said tube portion, said metallic liquid andsaid electrolyte being immiscible in each other and forming a singleinterface in said capillary tube; means for applying an electromotiveforce across said metallic liquid and said electrolyte effective tochange the interfacial tension between said liquids wherebyelectrocapillary movement of said single interface is induced; contactmeans having at least one movable element for actuating an electricalcircuit and translating means for moving said movable element responsiveto movement of said single interface including at least onesubstantially spherical ball made of a insulating material.
 7. Aswitching device according to claim 6, wherein said spherical ball islocated within said capillary tube portion, the diameter of said ballbeing less than said capillary tubes so that said ball may travellongitudinally within said capillary tube responsive to movement of saidinterface.
 8. A liquid-state switching device for electrical circuits,comprising: an envelope including a tube portion having capillarytransverse interior dimensions; a metallic liquid contained within saidenvelope and extending into said tube portion; an electrolyte containedwithin said envelope and extending into said tube portion, said metallicliquid and said electrolyte being immiscible in each other and having asingle interface in said capillary tube; a source of electromotiveforce; first and second substantially polarization resistant electrodesfor applying said electromotive force to and across said metallic liquidand said electrolyte respectively, said second electrode comprising acalomel electrode, whereby the interfacial tension between said liquidand said electrolyte is changed so that electrocapillary movement ofsaid interface is caused; and contact means having at least one movableelement actuated by said motion of said interface.
 9. A switching deviceaccording to claim 8, wherein said envelope includes a reservoir, andsaid electrolyte is contained within said reservoir and extends intosaid capillary tube, and wherein said second electrode has a secondinterface in said reservoir with said electrolyte, the surface area ofsaid second interface being large with respect to the first interfacebetween said electrolyte and said metallic liquid, whereby asubstantially non-polarizable electrode is provided.
 10. A liquid-stateswitching device for electrical circuits, comprising: an envelopeincluding a tube portion having capillary transverse and interiordimensions; a metallic liquid contained within said envelope andextending into said tube portion; an electrolyte contained within saidenvelope and extending into said tube portion, said metallic liquid andsaid electrolyte being immiscible with each other and forming a singleinterface in said capillary tube; means for applying a firstelectromotive force across said metallic liquid and said electrolyteeffective to change the interfacial tension between said metallic liquidand said electrolyte and cause movement of said single interface;contact means having at least one movable element actuated by saidmotion of said interface; and means effective upon removal of said firstelectromotive force for causing return movement of said interface to aninitial position occupied prior to application of said firstelectromotive force, whereby the response time of the switcHing deviceis improved.
 11. A switching device according to claim 10, wherein saidmeans for causing return movement of said interface includes means forapplying a second electromotive force across said metallic liquid andsaid electrolyte to cause movement in a direction opposite to said firstelectromotive force.
 12. A switching device according to claim 11,wherein said means for causing return movement of said interface furtherincludes resistance means in series with said means for applying asecond electromotive force of sufficiently high value that theelectrocapillary effect due to said second electromotive force isnegligible compared to the electrocapillary effect due to said firstelectromotive force when both said first electromotive force means andsaid second electromotive force means are operatively connected acrosssaid interface.
 13. A switching device according to claim 11, whereinsaid means for applying a second electromotive force across said firstand second liquids includes an electrical control circuit operativelyconnected to interlock said second electromotive force responsive toapplication of said first electromotive force and to apply said secondelectromotive force for a predetermined length of time responsive toremoval of said first electromotive force.
 14. A switching deviceaccording to claim 10, wherein said means for causing return movement ofsaid interface includes a resistance operatively connected across saidfirst and second electrodes.
 15. A switching device according to claim10, wherein said means for causing return movement of said interfaceincludes at least one quantity of gas contained within said envelope andoperatively associated with said interface to change volume responsiveto movement of said interface caused by said first electromotive forcemeans and to exert a reaction force on said interface effective to causesaid interface to return to said initial position upon removal of saidfirst electromotive force applying means.
 16. A switching deviceaccording to claim 15, wherein said quantity of gas is initially at apressure greater than atmospheric, and wherein movement of saidinterface responsive to said first electromotive force means compressessaid quantity of gas.
 17. A liquid-state switching device for electricalcircuits, comprising: an envelope including a tube portion havingcapillary transverse interior dimensions; a first conducting liquidcontained within said envelope and extending into said tube portion; asecond conducting liquid contained within said envelope and extendinginto said tube portion, said first and second liquids being immisciblein each other and forming a single interface in said capillary tube;means for applying an electromotive force across said first and secondliquids effective to change the interfacial tension between said firstand second liquids and cause movement of said single interface and saidfirst and second liquids; contact means having at least one movableelement actuated by said motion of said interface; and filter meansoperatively associated with said first and second liquids forrestricting said motion of said interface to said capillary tube.
 18. Aswitching device according to claim 17, wherein said envelope includesfirst and second reservoirs, said first reservoir is joined with saidcapillary tube at one end thereof and has a common fluid path therewith,said electrolyte extends into and partially fills said first reservoir,and wherein said second reservoir is joined with said first reservoirand has a common fluid path therewith, and further comprising a gasfilling said second reservoir, a first filter partition mounted in thefluid path between said capillary tube and said first reservoir andsubstantially separating said capillary tube and said first reservoirfrom each other, said filter partition being pervious to saidelectrolyte and impervious to said metallic liquid, and a second filterpartItion mounted in the fluid path between said first reservoir andsaid second reservoir and substantially separating said first reservoirand said second reservoir from each other, said second filter partitionbeing pervious to said gas and impervious to said electrolyte.
 19. Aliquid-state switching device for electrical circuits, comprising: anenvelope including a plurality of passageways having capillarytransverse interior dimensions; a first conducting liquid containedwithin said envelope and extending into the respective passageways; asecond conducting liquid contained within said envelope and extendinginto the respective passageways, said first and second conductingliquids being immiscible with each other and forming a single interfacewith each other in each of said plurality of passageways respectively;means for applying an electromotive force across said first and secondliquids effective to change the interfacial tension between said firstand second liquids at each interface in the respective passageways andcause movement of each said interface, whereby motion of said first andsecond liquids is caused responsive to motion of said plurality of saidinterfaces; and contact means having at least one movable elementactuated by said motion of said first and second liquids.
 20. Aswitching device according to claim 19, wherein each said capillarypassageway having one and only one interface between said first and saidsecond liquids.
 21. A switching device according to claim 19 furthercomprising filter means operatively associated with said first andsecond liquids for restricting said motion of said interface to saidcapillary tube.
 22. A liquid-state switching device for electricalcircuits, comprising: an envelope including a tube portion havingcapillary transverse and interior dimensions; a metallic liquidcontained within said envelope and extending into said tube portion; anelectrolyte contained within said envelope and extending into said tubeportion, said metallic liquid and said electrolyte being immiscible witheach other and forming a single interface in said capillary tube; meansfor applying a first electromotive force across said metallic liquid andsaid electrolyte effective to change the interfacial tension betweensaid metallic liquid and said electrolyte and cause movement of saidsingle interface; switching circuit means having portions located withinsaid envelope; and means responsive to the movement of said interfacefor changing the state of said switching circuit means coacting with theportions of the switching means within said envelope.
 23. A switchingdevice as in claim 22 further comprising a source of first electromotiveforce, said electromotive force applied across said metallic liquid andsaid electrolyte so that the electrolyte is positive with respect tosaid metallic liquid.
 24. A switching device as in claim 23 wherein saidmetallic liquid is mercury.